Lateral pelvic lymph node dissection based on nodal response to neoadjuvant chemoradiotherapy in mid/low rectal cancer: a retrospective comparative cohort study.

Total mesorectal excision (TME) without lateral pelvic lymph node (LPN) dissection (LPND) is feasible in patients with mid/low rectal cancer showing a reduction in LPN size to ≤5 mm following neoadjuvant chemoradiotherapy (nCRT). We aimed to evaluate the clinical outcomes of selective LPNDs based on these criteria. Patients with mid/low rectal cancer and LPNs >5 mm before nCRT were included and classified based on nCRT response (post-nCRT LPN size ≤5 mm [responsive] vs. >5 mm [persistent]) and surgical procedure (TME alone vs. TME + LPND). In the responsive group, LPND was selectively performed only if morphologic predictors of LPN metastasis were present. Clinical outcomes were analyzed across subgroups. Of 122 patients, 82 were in the responsive group. Within this group, 61 underwent TME alone and 21 underwent TME + LPND. No locoregional recurrence was observed in either subgroup of the responsive group, with similar systemic metastasis rates (13.1% vs. 14.3%, P > 0.99). The TME alone subgroup showed significantly smaller post-nCRT LPN sizes (1.7 ± 2.1 mm vs. 3.9 ± 1.8 mm, P < 0.001) and lower ycN positivity rates (31.1% vs. 71.4%, P = 0.001). Selective LPND based on post-nCRT LPN size ≤5 mm and the absence of morphologic predictors of metastasis may serve as a feasible option for managing mid/low rectal cancer with enlarged LPNs, thereby optimizing local control and reducing unnecessary surgeries.